1) If you don't mind the UAE heat, then at below 80 keep open the car windows and turn off the AC, above 80 kph rolls up the windows and utilise your car's AC (research air resistance and drag for the scientific discipline behind it)
2) Make sure your car's spark plugs are in A1 condition or use advance NGK or any other brands titanium tipped laser plugs
3) Make sure the car's air filter is clean or upgrades your car's air filter system
4) Upgrade your car's exhaust system, Do not use a noisy one or you will get fined approximately it's around AED 200
5) Use a good engine lubricant
6) Your tyre pressure needs to be correct, lower tyre pressure uses more fuel
7) Don't use car body kits as it changes the aerodynamics of the car and increases air resistance
Do not use over accelerate, getting to 120 kph quickly means using more fuel. (drive safe)
9) Drive around 110kph and you will be surprised at how much fuel you can save by just going 10 kph slower.
10) Most important - Make sure your next car is a hybrid

As and Engineer student who studied physics (I know u'll hate me for that ), Air friction is proportional to the speed at low speeds and the friction get squared (friction x friction, and u can imagine how big the number will be) at the high speed (the relationship stays the same as low speeds but with high speeds it become air friction^2 ∝ Speed)
Hopefully someone will understand a thing from that all xD